Larry King, the veteran US chat show host who claims to have conducted some 50,000 interviews in a broadcasting career spanning 53 years, is to step down from his nightly CNN show.

The broadcaster, noted for his penchant for wearing braces, made the announcement last night. He has presented Larry King Live for the past 25 years, and holds the Guinness world record for hosting the longest-running show on the same network in the same time slot, though ratings have recently been in decline.

King, 76, said he felt no pressure from CNN to leave, and that he was leaving to spend more time with his family. The host said he would remain at CNN to host special shows on "national and international subjects".

"Twenty-five years ago, I sat across this table from New York governor Mario Cuomo for the first broadcast of Larry King Live.

"Now, decades later, I talked to the guys here at CNN and I told them I would like to end Larry King Live, the nightly show, this fall and CNN has graciously accepted, giving me more time for my wife and I to get to the kids' little league games."

With cable news audiences gravitating towards politically opinionated shows, and newsmakers finding many more outlets for interviews, King has slipped behind rivals such as Fox News's Sean Hannity and MSNBC's Rachel Maddow in the ratings.

The New York Times recently reported that King's average nightly audience has halved since the last presidential election in 2008, to just 725,000 viewers.

King, who over the course of his career has interviewed every US president since Gerald Ford, began his career as a journalist and radio broadcaster in Florida before being wooed by CNN to host the nightly TV talk show in 1985.

CNN said King "defined the art of the television interview".

"His candour, curiosity and compassion are legendary, and his ability to interview people from all walks of life – world leaders, celebrities and everyday people – has made him an icon," it said in a statement.

King's soft questioning style has been pilloried by critics, but others argue his style also helps attract wary stars, such as Mick Jagger and Eric Clapton, who would be unlikely to be quizzed on challenging issues.

King said in an interview yesterday that he always tried to ask short questions, and never come in with an agenda. "I left my ego at the door," he said.

"I never learned a thing while I was talking. That would be my motto."